This invention relates to modem architecture for communication lines. More particularly, this invention relates to modem circuitry used in connection with isolation systems for connecting to phone lines.
New generations of consumer appliances like set-top boxes, payphones, vending machines and other systems often require or prefer low-speed data modems. Such modems allow remote hosts to handle billing or other housekeeping functions, or permit xe2x80x9csmartxe2x80x9d vending machines to call for more supplies. Although typical microprocessor and digital-signal-processor (DSP)-based multimedia chips employed in set-top boxes and other systems are capable of implementing a low-speed modem, they would do so at an undesirable manufacturing complexity and expense.
Prior modem architectures typically included multiple integrated circuits for handling modem processing and communication line termination. In particular, one or more digital-signal-processor chips have been coupled to analog-front-end circuitry, which in turn has been connected to line termination circuitry across a transformer isolation barrier. Such modem architectures suffer from numerous disadvantages.
The present invention provides an improved modem architecture and associated method that integrate modem functionality and line-side isolation functionality while also providing flow control of internal data between an isolation interface, digital-signal-processor (DSP) circuitry, and an analog input.
In one embodiment, the present invention is an integrated modem and line-isolation circuit including system-side line-isolation circuitry capable of being coupled through an isolation barrier to a communication line, digital signal processing (DSP) circuitry integrated with the system-side line-isolation circuitry, isolation interface circuitry within the system-side line-isolation circuitry adapted to be coupled to the isolation barrier, an analog input, and path control circuitry coupled to the analog input, the isolation interface and the DSP circuitry, the path control circuitry having a control signal that determines flow of data between the analog input, the isolation interface and the DSP circuitry. In addition, the DSP circuitry has a modem processor for modem data and a digital processor for system-side circuitry. In a more particular embodiment, the integrated modem and line-isolation circuit may also have an analog output coupled to the path control circuitry, where the control signal determining the flow of data between the analog input, the analog output, the isolation interface and the DSP circuitry. Still further, a digital-to-analog converter may be coupled to the analog output, and an analog-to-digital converter may be coupled to the analog input. In addition, the path control circuitry may include a plurality of switches controlled by the control signal, and the control signal may be a multiple bit signal from a programmable register.
In another embodiment, the present invention may be a method for controlling data flow in an integrated modem and line-isolation circuit including providing a system-side line-isolation integrated circuit having digital-signal-processing (DSP) circuitry having a modem processor for modem data and a digital processor for system-side circuitry, providing isolation interface circuitry within the system-side line-isolation circuitry adapted to be coupled to the isolation barrier, providing an analog input; and controlling the flow of data between the analog input, the isolation interface and the DSP circuitry. In a more particular embodiment, the method may also include providing an analog output and controlling the flow of data between the analog input, the analog output, the isolation interface and the DSP circuitry.